The special dry warm wind that blows from the Rocky Mountains down into valleys below is called a Chinook wind.

Here are some key characteristics of a Chinook wind:

* Warm and Dry: They are significantly warmer and drier than the surrounding air.

* Descending Air: They are formed when air descends the eastern slopes of the Rockies, compressing and warming.

* Rapid Temperature Changes: Chinooks can cause dramatic and rapid temperature increases, sometimes within a matter of hours.

* Snow Melting: The warm, dry air can melt snow and ice quickly.

* Common in the Western US: They are most common in the western US, particularly in Montana, Wyoming, and Colorado.

Let me know if you'd like to learn more about Chinook winds!